Light direction assemblies are devices used in several applications, such as a display, digital projector, or other imaging systems, for directing and positioning a light image onto a display medium such as a screen. Each of these light direction assemblies may include what are commonly known in the art as tip-tilt platforms that are rotated or moved to direct light and project an image onto a viewing medium. The light directed by the light direction assemblies may either be reflective or refractive. In the case of a reflective tip-tilt platform, a light directing member, such as a mirror, reflects substantially all the light that is incident thereon. Other light directing members control the position of the projected image by refracting light that passes therethrough such as in the case of transparent glass.
The position of a projected image may be controlled by controlling the positioning of the light directing member. The positioning of the light directing member may be controlled by an electromechanical actuator, such as what is known in the art as a wobulator motor. The electromechanical actuator responds to changes in current flow through the actuator's coils. The light directing member, in turn, is rotated or moved in response to the change in flow of the current through the controlling actuator. The faster the rate of change in the current flowing through the coils, the quicker the light directing member can be positioned and repositioned to project an image. The quicker the change in positioning of the light directing member, the higher the quality and the sharper the projected image will be to the viewer. This technique of positioning and repositioning a light directing member at a fast rate (between 60-240 cycles per second in some embodiments) to project an image is known as wobulation, which is described in the following two patent applications: “Image Display System Method”, Ser. No. 10/213,555, and “A Two-Axis Tip-Tilt Platform”, Ser. No. 10/789,255.
The coils employed by the actuators to flow current typically have a high inductance, as a direct result of the number of windings in the coil, making it difficult to quickly change the rate of current that passes through the coils. A fast rate of change of coil current is needed for swift and accurate motion of the electromechanical actuators. An increase in voltage is typically used to force the desired amount of current through the coils. However, higher voltage sources may add costs as well as present potential regulatory compliance issues.
The embodiments described hereinafter were developed in light of this situation and the drawbacks associated with existing systems.